This invention relates to a socket wrench for rotating a spark plug, more particularly to a socket wrench device which can move a spark plug to a predetermined position in the cylinder of an internal combustion engine.
Referring to FIG. 1, the externally threaded portion 3 of a spark plug 1 is engaged within the threaded hole 4 of a cylinder cover 2. A hexagonal casing 5 is provided on a portion of the insulator 6 of the spark plug 1 so that a socket wrench can rotate the spark plug 1. Because the operator cannot accurately control the torque to tighten the spark plug 1 against the cylinder cover 2, the spark plug 1 may be overly or insufficiently tightened. In a situation where the spark plug 1 is too loose, the combustible mixture cannot be ignited thereby. When the spark plug 1 is too tight, the combustion chamber of the associated engine overheats, thereby resulting in damage to the electrodes of the spark plug 1. Furthermore, the excessive tightness of the spark plug 1 breaks the threads of both the spark plug 1 and the cylinder cover 2.